Internal-combustion engine



June 30, 1953 J. HITTELL 2,644,021

INTERNAL-COMBUSTION ENGINE Filed March 7, 1946 15 Sheets-Sheet 1 I FiqJ.

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INTERNAL-COMBUSTION ENGINE Filed March 7, 1946 15 Sheets-Sheet 3 \L K I Q INVEN TOR.

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INTERNAL-COMBUSTION ENGINE Filed March '7, 1946 15 Sheets-Sheet 4 1N VEN TOR.

June 30, 1953 J. L. HlTTELL 2,644,021

INTERNAL-COMBUSTION ENGINE Filed March 7, 1946 15 She.ets-Sheet s IN VEN TOR.

June 30, 1953 J. HITTELL 2,644,021

INTERNAL-COMBUSTION ENGINE Filed March '7, 1946 15 Sheets-Sheet 6 IN VEN TOR.

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. INTERNAL-COMBUSTION ENGINE Fild March 7, 1946 15 Sheets-Sheet 9 June 30, 1953 J. L. HITID'ELL. 2,644,021

INTERNAL-COMBUSTION ENGINE Filed March 7, 1946 15 Sheets-Sheet l1 lNVENTOE 324 334 335 R 21 2 June 30, 1953 J. L. HITTELL 2,644,021 INTERNAL-COMBUSTION ENGINE Filed March 7, 1946 15 Sheets-Sheet l2 June 30, 1953 J. HITTELL 2,644,021

INTERNAL-COMBUSTION ENGINE Filed March 7, 194 15 Sheets-Sheet 15 Fjq. 28. W

Patented June 39, 1953 UNITED IN TERNAL- COMBUSTION ENGINE John Lindsay Hittell, Livonia Township, Wayne County, Mich.

Application March 7,1946, Serial No. 652,678

27 Claims. 1

This invention pertains particularly to structures cooperating to improve efiiciency, durability and adaptability of such engines by providing means for successful operation at variable displacement, and for improved compression ignition operation.

One object of this invention is to provide automatic means for controlling the variable displacement of the engine and to have this means operate in accordance with the amount of power the engine is being called upon to produce by the combined action of the operators control of the throttle and the load on the engine.

It is a further object to provide speed limiting control devices capable of limiting the engine speed to a certain value at full displacement but allowing increase of this speed in accordance with increased safe operating speed at reduced displacement and speed responsive means for advancing injection timing as the engine speed is increased and to provide an engine with novel valve mechanism capable of satisfactory and enduring operation at ultra high speeds when operating the engine at reduced displacement.

Another object of this invention is to provide improved means of fuel injection capable of maintaining an ultra fine degree of atomization even at cranking speeds and also capable of metering the fuel injected per cylinder stroke in l more exact proportion to the weight of air taken into the cylinder under wide variations of operating conditions.

A further important object of this invention is to provide means for maintaining consistent accuracy of fuel metering under variations of fuel viscosity and wear of parts by completely eliminating leakage through sliding or running fits as a factor affecting fuel metering, and further to avoid likelihood of the fuel becoming mixed with lubricating oil by avoiding any reliance on the ability of any rotating or sliding fit to keep the fuel and lubricating oil separated. These two features avoid the need of ultra-fine fits heretofore found to be absolutely necessary in high pressure fuel injection equipment and usually a cause of high manufacturing costs and considerable service trouble on account of sticking due to microscopic dirt particles, thermal expansion, surface growth or even slight gum or lacquer formation, or leaking beyond a tolerable amount due to even very slight wear.

Other objects are to provide fuel injection means unusually free from external pipingand high pressure joints, to provide short lines free from harmful resonant conditions even at ultrahigh operating speeds, and to provide for removal of injectors for test or replacement without disturbing any piping.

A further object of this invention is to widen the range of fuels which can be used with full satisfaction in a compression ignition engine by providing an injection system able to properly meter and atomize fuels of widely differing distllling ranges, even as light as gasoline, and to handle fuels of low ignition quality by operating at high compression pressures and temperatures and by maintaining fine fuel atomization under all operating conditions, especially at cranking speeds.

A more general object of this invention is to provide numerous new features contributing greatly to overall performance, long life and easy servicing of internal combustion engines and to devise and combine same in such compact, light weight and economicalto-manufacture form and arrangement that the savings thus accrued make possible the inclusion of these numerous improved features without increase in cost.

Further objects of this invention are such as may be attained by utilization of the various combinations, subcombinations, and principles hereinafter set forth in the various relations to which they may be adapted without departing from the spirit of my invention, as set forth more particularly in the following detailed disclosure of the preferred embodiments and in the terms of the appended claims.

Referring to the drawings:

Fig. 1 is an exterior plan view of the engine showing also, somewhat diagrammatically, the principal accessories.

Fig. 2 is a vertical section through the complete unit along line Z-2 of Fig. 1. Certain parts having the interior detail too fine to show clearly in this figure are shown in exterior view and shown in detail sections to a larger scale in other figures.

Fig. 3 is a partial horizontal section stepped as indicated by line 3-3 of Fig.2.

Fig. 4 is a partial vertical section through the lower portion of the mechanism as indicated by line i-A on Fig. 3.

Fig. 5 is a vertical section through the lower portion of the mechanism, along line 55 of Fig. 3.

Fig. 6 is a horizontal section through a lower portion of the engine along line 66 of Fig. 5.

Fig. '7 is an enlarged partial section through the engine base along line 1-1 of Fig. 3 and 2-2 of Fig. 1 showing detail not shown in Fig. 2.

Fig. 8 is an-enlarged vertical center line section through the fuel pump along line 8-8 of Fig. 3.

Fig. 9 is a vertical center line section through the fuel control box along the radial line {3-9 of Fig. 1.

Fig. 10 ,is a horizontal section through fuel control box substantially along line ifi--l0 of Fig. 9.

Fig. 11 is a vertical section through the fuel control box along line Hi ll of Fig. 9.

Fig. 12 is an end view of the extending portion of the fuel control box viewed as indicated by the line I2I2 of Fig. 9.

Fig. 13 is a view of some of the fuel box parts removed from the rest of the mechanism.

Fig. 14 is a stepped horizontal section through the engine head along line 16-44 of Fig. 2.

Fig. 15 is a vertical partial section through the engine head along a radialline 15-15 shown in Fig. 14. This is a typical section repeated in most respects in 6 other corresponding positions. The variations involved are shown in other views, particularly in Figs. 1, 2, 9, and 14.

Fig. 16 is a horizontal section through the top portion of the engine along line I6l6 of Fig. 2.

Fig. 17 is an enlarged partial vertical section substantially along line lli'l of Fig. 1. lhe

governor mechanism is here seen out at a right s angle to the way it is shown in Fig. 2.

Fig. 18 is a partial horizontal section showing detail along line [8-48 of Fig. 2.

Fig. 19 is also a partial horizontal section showing detail along line l9l9 of Fig. 2.

Fig. 20 is a partial horizontal section along line 2fi2l of Fig. 2.

Fig. 21 is a partial vertical section taken on a plane at substantially forty-five degrees to the plane of Fig. 2 along line 2l-2l of Fig. 18.

Fig. 22 is a partial horizontal section along line 2222 of Fig. 2.

Fig. 23 is a section through valves and valve mechanism along line 2323 of Fig. 22.

Fig. 24 is a much enlarged partial section through the centerline of the injector showing detail omitted from Figs. 2 and 17.

Fig. 25 is a view of a modified form of injector and injector shell.

Fig. 26 is a .sectional view through centerline of same as indicated by line 26-26 of Fig. 25.

Fig. 27 is a partial View and section along line 21-47 of Fig. 2.

Fig. 28 is an enlarged partial section along line 2-2 of Fig. 1 showing details of rings, and upper connecting rod end ball joints, and showing also a modified form of piston particularly suited to this engine. 7

Fig. 29 shows a section along line 2929 of 1 Fig. 28.

Fig. 34 is a section through the injector shown in Fig. 24 along line 3fi34 of Fig. 24.

. ranged in a circle about the main axis and approximately parallel thereto.

Such an engine in small sizes may preferably be embodied in three cylinder form, while for engines of intermediate sizes such as are commonly used in self propelled road vehicles a seven cylinder construction is preferred and selected for illustration in this preferred embodiment, while for other uses five or nine or more cylinders might be more suitable.

'form concentric spherical surfaces.

In the seven cylinder engine herein described in detail and shown in the drawings, a base casting I serves as a general framework and housing in or upon which most of the apparatus is mounted. Referring initially to Fig. 2, an engine cylinder block 2 is mounted on the base I and retained thereon by cap screws la. The cylinder block carries liners 3 suitably fitted in the block at the top and bottom. Pistons d reciprocate in these liners and carry rings 5 for sealing the compression and firing pressures.

Tubular connecting rods 6 each have two cupped ends accurately finished inside and out to The lower end of each rod rests on a pressure block I and is held by retainer 8. The retainers and pressure blocks each have spherically finished surfaces mating with the spherical surfaces of the rod end to form a spherical bearing permitting the rod to swing to a limited angle in any direction. The blocks 1 rest on the upper plane surface of a rocking member 9 and are held against shifting by means of integral tubular extensions IO projecting upward from the plane surface of member 9. The retainers 8 also rest on the plane surface of rocking member 9, and are held thereto by bolts H. A similar type of joint at the upper end of the rod allows same to also swing at limited angles to the axis of the piston in any direction.

A displacement control member i2 is slidably fitted in a large bore in base casting i and has a smaller diameter portion extending downward into and also slidably fitting in a smaller bore in this casting. An annular piston is is affixed to the displacement control member by cap screws i4 and is slidably fitted in a larger bore in casting I and sealed by a ring l5. A ring it also seals the large diameter portion of control member 12 to complete the sealing of an annular chamber ll. When oil under pressure is admitted to chamber I? it thus tends to raise the control member toward its uppermost position, in which it is shown.

Formed integrally with the upper end of the control member I2 is the inner member of an improved type of constant angular velocity universal joint. A number of ball races 12a are formed in the periphery of this portion with lands between these races forming partial spherical surfaces concentric with the point X and also with the main vertical axis. A thrust and centering member 122) is snugly fitted to the extreme upper end of member l2 and has a spherical surface, bearing against a concave spherical washer 18. A ball retainer and aligner [9 has an internal cylindrical surface in rocking contact with a portion of the lands between the said races I2a and a concentric exterior spherical surface in rocking contact with the central portion of the rocking member 9 which also has formed therein internal races 9a for the balls 20. This forms a constant angular velocity universal joint of a general type that is known, but I have devised certain improvements which will be more fully described hereinafter.

It is evident that a geometrically correct constant angular velocity universal joint in this environment serves to permit the rocking member 9 to rock about point X either fore and aft or left and right or any combination thereof without disturbing in the slightest way the angular position of the rocking member 9 about its axis along the line X-Y. The control member [2 and piston 13 are prevented from being rotated by torque reaction by three extensions its on piston i 3 which register with three bores in casting Two angular contact ball bearings are mounted on the inner portion of rocking member 9 and retained by nut 22 and lock wire 23, and a flywheel 24 is mounted on the outer races of these ball bearings, and retained in position thereon by cap ring 25 and bolts 2E5. One end of a link 27 is hinged to flywheel 24 by means of a pin 28 and a pin 29 through the other end of the link and through a shaft 3c hinges the upper end of the link to the shaft 36 on an axis intersecting the axis of the shaft. The flywheel 2 has an internally splined hub mating with an externally splined portion of a shaft 3i and is held in position thereon by a nut 32 which also retains a washer 33 which carries short splines to mesh with'those on shaft 35 to hold this washer against turning so that an integral cam portion 3A? is held in proper position to enter a slot pro vided in the link 2?. The spiines on flywheel and shaft 39 also permit a pin 35, which is fitted in the lower end of the shaft 31 and the upper end of a power take-off quill shaft 37 and retained by lock rings 36, to be held parallel with pins 28 and 29.

It may now be noted that this construction permits the flywheel 2 3, the link 21, and the shafts 30, 3!, and 31 to all rotate a unit about the axis of shafts 3i? and 37, carrying with them, of course, all the directly attached parts. This rotation carries the outer races of the ball bear ings 2! in rotation about the main axis also, and

since these ball bearings are at an angle, with the high point aligned with the link 217, the rocking member 9 is forced to rock about the point X as the above described parts rotate, with the result that rocking member 9 has its high edge follow around with rotation of the low end of link 27, but does not rotate at all, being held from rotation or even small angular oscillation about its axis X--Y by the balls 28 and their cooperating races. Accompanying this motion of rocking member 9 the pistons reciprocate in the cylinder liners 3 an amount that is governed primarily by the radius of the lower spherical center lines of the connecting rods (:3 from the axis X--Y and by the angle of tilt of the bearings 2 i.

It now becomes evident that if the point X is lowered, keeping the center line of pin 29 at the same level, the angle of tilt of the bearings 2i is increased, and thus as point X is lowered the stroke of the pistons is thereby increased.

It might at first appear that lowering of point X would cause the upper limit of the stroke to be raised while the lower limit is being lowered, but this is not the case, since as point X islowered the center line of pin 28 is also lowered to a lesser degree with the result that the top point of the stroke is made to lower slightly as the bottom point is lowered to its maximum stroke point.

By proper positioning of the pins 28 and 29 in relation to the high and low positions of pin 35, accompanied of course, by suitable length of link 21 and of connecting rods and pistons in relation to piston head clearance, it is possible to hold a compression ratio of 15 to 1 at full diplacement and at two-thirds of full displacement and then to have the compression ratio increase to approximately 16 to l at one-half displacement and to approximately 20 to 1. at one-third of full displacement.

It has been most simple to explain the action of this mechanism starting from shaft rotation and developing the accompanying piston travel which is of course the true case when starting or when the flywheel is carrying a cylinder up its compression stroke. However the mechanism is fully reversible and the power of the firing strokes is delivered to the quill shaft 3? simply by reversing the travel of the forces from part to part.

The quill shaft 3'! is mounted at its lower end in a ball bearing 38 supported inside the lower portion of control member I2. This bearing serves primarily as a thrust bearing, and is retained by a nut 39 and lock means 49 so that it is able to draw down on the quill shaft 3?, and through the shaft 3i, flywheel 24' and bearings 2| is able to hold the spherical surfaces of elements !2b and I 8 in close running contact so that they serve to center the revolving and rocking mechanism in relation tothe upper portion of control member 52. This also centers the shaft 3! and the upper end of the shaft 31, which may have a considerable clearance in the bore of the control member I2. v

The quill shaft 31 is slidably 'splined to the upper portion of a shaft 4!. A short quill shaft 42 surrounds and is splined to a lower portion of the shaft 4! and has a spiral bevel gear 23 formed integrally. A small gear 44, carrying a bearing 45 is fitted and splined to the lower end of the shaft 4! (Fig. 5). A nut 35, with lock means ll, holds the gear M, the bearing :35, and the quill shaft 42 firmly against a shoulder :38 on the shaft M, thereby positioning the shaft 4! in relation to the shaft 42 which is mounted in a bearing re. The bearings 45 and 49 are mounted in a bear-- ing plate 50] which is also bored to form a close running fit for the shaft 32.

The bearing plate 50 has ports 5! milled therein, and the shaft 52 cooperatesto act as a rotary valve by means of ports 42a (Figs. 5 and 6) milled therein and a communicating annular port 52 3. A pump body 52 fits closely over the hub of the bearing plate 53 and has a gear chamber and a bearing for a gear pump gear 53 which has an in tegral shaft and is driven by a gear 5% splined thereto and driven by the gear 44. The pump gear 53 meshes with two similar integral shaft pumping gears 55 (Fig 6), and the gears 53 and 55 are covered and retained by a pump cover 5 5 which also fits closely on and is located by centering on the hub of plate 5! A pin 5? (Fig. 2) gives the additional locating point required to keep the pump casing parts in full alignment. An outlet passage 58is cored in the pump body 52 and discharge ports 58a (Fig. 6) provide communication between passage 58 and the chamber in which the pumping gears operate. The cover 56 has cored therein an inlet manifold 59 and ports which open into the pumping gear chamber. Passages 68 admit oil from the oil reserve space immediately above in the base casting i through tubes fifia which are provided to cause the oil to be taken in above the sediment level.

The base casting l is machined to locate and mount thebearing plate 50 which is held in position by cap-screws SI and by longer cap-screws 62 which also serve to clamp the pump body 52 and cover 56 in position. Also four cap-screws 62a hold the pump casing parts together but do not enter casting I, so that the pump assembly may be removed as a unit if desired. An additional nut 46a and lock means Ma are used to hold gear 54 in position. The oil pump assembly above described is closed in by a cover 53, sealed by a gasket 64. Screws and lockwashers 65 hold the cover 63 in position.

acagoei The oil pumpdischarge passa e 58 communi cates witha passage 68. through, a. port 50a (Figs. 5 and 6), and the passage 68 delivers oil to an annular space 69 around a valve sleeve To which is stationary. Slidably fitted aroundthe upper part of sleeve I is a relief valve 1 I, held down by a spring 12 which bears against a shoulder on valve H which is slidably fitted in base casting I. Fig. shows the valve H at its operating point, that is just cracked. If raised slightly from this position by increase in pressure in annulus 69, oil is, passed between parts Ill and N, then through apertures 73, thence around a displacement responsive member (4 and through a perforated spring-seat washer l5 and passages Ti into the chamber (1, Three. springs 76 are fitted in three extensions lid of piston 13 and are proportioned to lift this piston and the weight of the attached parts when. there are no pressures in the engine. One of the springs I5 holds the Washer 15 seated. I

The space in which spring l2 operates is vented to atmospheric pressure through a vent l3, consequently the operation of the valve is. controlled exclusively by variations in gage pressure in annulus 69 therefore it functions directly to regulate this pressure and is not influenced by the fact that the escape of oil into chamber ll as above described provides a useful outlet for this oil, using it at a lower pressure rather than letting it escape to atmospheric pressure. The pump gears 53 and 55 are so proportioned that the quantity of oil delivered is sufficient to keep a small amount. of oil passing through valve i! atall times, but at times when i mes necessary or desirable to reduce the displacement of the engine the other uses of oil, are less than normal so that a. larger supply of oil for chamber H is always available when expanding of th s ch mb is necessary. It should be understood that this only insures supplying an adequate quantity or" oil to. chamber I1, and does not act tov control the movement of. control member l2 or piston l3, as this is controlled by governing the pressure maintained in the chamber H by means of a pressure governed valve which so adequately regulates the rate at Which the Oil is allowed to escape from this chamber that the rate of oil supply does not have any appreciable efiect on the pressure.

A fitting l9 conveys oil into a tube 88 at the pressure controlled by the valve H, and oil at this pressure is also admitted to the annular space around a spool valve 8i through ports 82 in sleeve 10.. A spring 83 presses down on the valve 8! and its upper end is seated in the displacement responsive member 1d. The valve BI is shown in its cracked position, and the spring 83 is so proportioned that the force it exerts, on the valve 8| as it holds this position is varied by vertical movement of member 74 to keep this force proportional to the displacement of the engine. An annular chamber 84 below valve 8! exposes a main portion of the lower area of valve 8! to the pressure of the oil. in chamber 84. Since the oil supply pressure is, balanced as to its effect on the position of valve 8!, and atmospheric pressure is maintained in. the chamber above by venting through the center of the valve 8i to it lower end and thence to atmosphere, the position of valve 8! is under the exclusive control of the force applied by Spring 83 and the upward force exerted by pressure. of oil in chamber 84. When these forces are balanced the valve 89 thus. stays in cracked position as shown, while any drop in pressure in chamber 84 causes the valve to be lowered and. admit more oil from the. high pressure, supply torestore a balanced condition, while if the pressure in chamber 84 should become too high the passage from the supply into chamber 84 is entirely closed off and thus the use of oil from chamber 84 returns the balanced condition. Therefore, with adequate supply pressure, the pressure in chamber 84 is maintained proportional to the displacement even under considerable variations, in the flow of oil permitted from chamber B l.

Passages 35, through sleeve 70 convey oil from chamber 84 into a passage 86' in the base, casting through a port 81 and a cored passage 38 into an annular groove 89 and ports 99 in bearing plate 50. As shaft 42 rotates, the ports 42a therein. thus alternately connect the groove 42b with the ports 98 and 5|, thereby causing the pressure in groove 62b. to vary from atmospheric when connected to ports 5,1,, to a pressure closely approaching the controlled pressure prevailing in chamber 84 when connected to ports 96. A port 9i through the hubv of bearing plate 53 connects the groove 42]) with a passage 82 through pump body 52 and a passage 93 (Fig. 3) through the pump body 52, hearing plate Ell and base casting l to a port 94 in a pad 95.

The fuel, pump assembly shown in Fig. 8 is attached to the pad 95 by screws 98. Fuel is supplied from a tank 9;! through a tube 98 and a soft synthetic rubber tube 99 which is fastened to a fuel pump. body 168 and to the tube 98 by clamps I81. In the pump body We is a bellows it? climbed and ard soldered to a mounting plate 183 which, is set into body Hi3 and sealed with soft solder or oileproof cement let. A light spring in, the form of a waved washer $95 supports a ring suction valve Eli against a valve plate l9? having a series of inlet perforations arranged in a circle above the suction valve ill-5 and another ring of perforations which are covered by a discharge valve N18.

The working surfaces of valves Hi5 and we and valve plate in? are preferably lapped smooth and flat, but the flexibility of the valves may be such that they need only be truly flat when pressed into working position by the pressures available in use. The valve SE38 is seated by a waved washer spring lflba.

An upper bellows IE9 is crimped and hard solder sealed to a mounting piece H0, then mounted in a shell Hi, and retained by a lock ring H2. Movement of the free end of the bellows C09 is limited by a stop plate H3 retained by a lock ring H l. This assembly is then sealed under gas pressure by soft soldering apassage 5 ita. The, gas should be non-oxidising and noncondensing at ordinary temperatures such as nitrogen or helium for examples, and the sealed pressure should be somewhat less than the minimum pressure which is to prevail in chamber 84 at minimum displacement. The bellows should be of suitable proportions as related to the compressibility of the enclosed gas to then stand a considerable number of flexings to the point it will take when the maximum pressure available in chamber 84- is applied in the space surruondin it. The mounting piece H0 is made to fill a large proportion of the space within bellows I69 to reduce the total stroke of the bellows under the range of pressures to which it is subjected in service.

The shell Ill and two gaskets H5 are then ped between a flanged cap I it and the pump body by screws H! and lockwashers H8 thus also clamping a gasket H9 and the valve plate HIT. A stop pin lZt is affixed to the valve plate it! and serves to limit the stroke of bellows 102 to a safe value for a moderate number of cycles. An accumulator check valve i2! is pressed against the top of the shell 5 i i by a waved washer spring E22, and opens under pressure diiierence to permit fuel to pass into the discharge opening in the top of flanged cap H5 and through a fitting I23 into a discharge line tube i2 3.

Referring again to Fig. 5 the smaller diameter portion of the valve 8i is a sliding fit in a spacer I25 which also acts as a lower stop for valve 8! when there is no pressure in chamber at. cross slot in the spacer :25 vents the small diameter end of valve 8! to atmospheric pressure through the passage H25 in the base casting i into a dry sump space I27. Oil leaking through fits in the valve mechanism as well as miscellaneous leakage in other parts of the unit may be drained into the space 62?, particularly from sections where it is desired to avoid excess oii accumulating.

When oil drained into the space l2? reaches a level above the bottom face of gears i t and St a certain part of this oil runs into the gear teeth as they are about to mesh, and some of this oil is forced upward against the bottom face of the hub of bearing plate 58 which is in free running contact with the tops of these gears. A port 828 (Fig. 2) is provided in this face just above the closing mesh point of the gears and receives oil at an appreciable pressure. The port I28 communicates with a groove 29 and a port I36 in the bearing plate hub and then through an angular passage 53! which joins a vertical passage 532, which registers with a continuing vertical passage I33 through base casting l and bearing plate 58. This chain of passages serves to convey oil from the mesh of the gears up to the top of passage 533 Where it flows down into the oil reserve space in the base casting. Any rise in the oil level in space 12? increases this flow, which is adequate to keep the space E27 cleared of all oil except an amount to keep the L gears Well lubricated.

I have found in practice that an open gear pump of this character will pump more effectively when the gears are helical. Oil trapped in the teeth of helical gears travels axially along the meshing teeth toward th last ends of the teeth to mesh. Since the rotation of shaft M is counterclockwise when looking at the top end, the gear t t has a left hand helix and the gear 56 a right hand helix as indicated by the diagonal lines near the mesh point of these gears in Fig. 2.

- means which have been described and is provided with an outlet port :34 and a pressure governed valve (Fig. 7) comprising a valve shell H35 in which is slidably fitted a valve I35 which is arranged to uncover several large ports iBl when moved downward. The valve I35 is supported on a light spring !38 which is seated at its lower end upon a stationary member I39 which is tightly fitted in sleeve I35 and is prevented from being forced down by fluid pressure by a lock ring Hill. The member I39 is axially bored and counter-bored to provide two diameters as shown, and a pilot valve Ml, having two corresponding diameters is slidably fitted therein. Th valve MI is pressed downward by a suitably proportioned spring M2 retained by a plug lit sized for a firm press fit into the upper portion of member ltd. An annular passage t lt admits oil from port 3 5 to cross passages 555 which convey it to an annular space around valve l4! and from there out through ports M6 when the pilot valve at its downward position as shown. This applies the pressure being carried in chamher ['1 to the entire lower end'area of the valve Vent passages it? connect the upper side of the shoulder area to atmospheric pressure, so long as pilot valve It! remains in th position shown the ports I31 remain covered since the pressure carried in chamber i? is strongly urging valve H36 upward since it is applied to a larger area below than above this valve.

However if the pressure in chamber ii rises sufficiently this pressure acting on the exposed under area of the larger diameter portion of pilot valve I41 will cause a force upward exceeding the downward force applied by spring Hi2, moving valve Mi upward to a point where ports its are sealed from the supply pressure and act to exhaust oil from under the valve I35 into the space around the lower portion of valve Ml. Ports i 38 and H39 then convey thi oil from there to the general oil reserve. This causes pressure of oil on the exposed upper surfaces of valve [35 to quickly move it down to completely uncover the ports it? providing an ample outlet from chamber ll.

Since asubstantial portion of the force resulting from the pressure on top of the engine pistons i is transferred, through apparatus that has been described, to the piston l3 and thus places the oil in the chamber it under pressure, a suitable pressure applied to the pistons 4 will cause the valve i l! to act as above described and the ports it]? will rapidly discharge oil until the pressure on the pistons is reduced or the control member if! has reached its extreme bottom position stopped by resting on the central portion of base casting i. The port Hit is so positioned that it is only slightly open when the control member i2 and piston i3 reach their bottom position, thus slowing up the last part of the downward travel to avoid shock when the stop is reached. When a suitable pressure on the pistons is exceeded thedisplacement of the engine may therefore be very rapidly increased, but the rate of decrease is limited by the amount of oil spilled to chamber ll by the valve ii. The direction of movement of the displacement control member is however determined entirely by whether the pressure in chamber I7 is over or under a certain critical value, with the pressure in chamber A? in turn determined by the pressure applied to pistons t.

The pilot valve Ml may hover at a mid-point when the pressure in chamber ii is being held at a certain value, and then the Valve I35 will settle in a position where the ports ltl are open just sufficiently to outlet the oil that is being admitted to chamber H by the valve "it, thus maintaining the critical pressure.

The average pressure applied to all the pistons t, which may be called the mean working pressure,'depends mainly on the pressure of the air in the intake manifold, and on the amount or" 

